In attempts to enhance secure identification of individuals many identification (ID) cards have been created using smart chips (such as U.S. Pat. No. 5,477,039, issued Dec. 19, 1995 to Lisimaque et al ). These chips optionally contain data storage that holds the individual's biometric date such as facial images, fingerprints, or retinal scans (such as U.S. Pat. No. 5,717,776, issued Feb. 10, 1998 to Watanabe, U.S. Pat. No. 5,787,186, issued Jul. 28, 1998 to Schroeder, and U.S. Pat. No. 6,219,439, issued Apr. 17, 2001 to Burger). To obtain entry to secure area, the individual is required to insert his/her card into a reader. The reader reads the biometric data contained on the chip and performs the detailed biometric test on the individual via devices that can read fingerprints, retinal scans, or other identifying biometric characteristics. The systems may provide very high security in areas where positive identification of the individual is required; however, the biometric readers are both expensive and complex. Such systems cannot be used reliably in high-volume areas, with many transient employees, or applications requiring routine positive identification for entry to the secure area without great cost such as airport entrances, or access to air traffic control rooms, or medium level security areas.
Other ID cards have named account numbers and other personal information encoded, either on a chip, or use a short range passive RF link, or alternatively a magnetic stripe card may be inserted into a reader capable of reading this information. In turn the individual may be asked to enter a personal identification number, or what is commonly called a PIN, on a door's keypad to obtain entry into a secure area (such as U.S. Pat. No. 4,839,506, issued Jun. 13, 1989 to Homma et al). In many other cases, a simple keypad is placed on the door and a code must be entered into the keypad to allow entry without a separate card (such as U.S. Pat. No. 4,887,445, issued Dec. 19, 1989 to Beatty, U.S. Pat. No. 3,953,769, issued Apr. 27, 1976 to Sopko, and U.S. Pat. No. 5,704,151, issued Jan. 6, 1998 to West et al, relating to a keypad on gun lock)). These keypad approaches provides only limited security when many individuals in high-volume areas such as airports, or office doors.
One major problem with systems that use a keypad located at the door, is that the codes must be frequently changed and distributed to many people on a weekly or daily basis. This process leads to significant security risks because the codes are often written down and provided in e-mail or memorandum form for the benefit of authorized individuals. It also becomes necessary to change the code whenever even a single individual leaves the employment of the company using such a keypad-guarded door. An alternative approach is to use a door with many different codes, one for each individual making use of the door. In that case, only a single code must be changed if an individual leaves employment of the company. However, as the number of codes that are capable of opening the door increases, the security level of entry decreases. In the simple case, if the door has three buttons labeled 1,2,3 and a code of only three digits for use (e.g. 3,2,1), the likelihood of entry by an unauthorized intruder is one out of nine, since there are only nine possible combinations. If the company wanted to provide unique access to four employees, giving each a unique code, the likelihood of entry by a non-authorized intruder now rises to four out of nine. In other words, an intruder enjoys almost a 50% probability of guessing a code that would allow unauthorized entry, and the security level of the door is therefore significantly decreased.
A third method of secure access, is simply to have a physical card with optional identity information associated with the card. For example, a picture, or the individuals name and address. The card may be placed in a reader to obtain access, or in some cases may transmit a signal to a reader that might open a door. The same system is used widely for automobile entry, where small “keyfobs” are used to transmit a unique signal to an automobile to open the doors and in some cases start the automobile. Again these wireless “keyfob” security system depend only upon holding onto (and not losing) a physical device to obtain entry and no independent checks of the person's actual identity or authorization to use the card or “keyfob” can be made. The security in this case is similar to the security afforded by the usual metallic mechanical key, which can be duplicated, and provides no assurance that its holder is authorized for entry.
Finally, a similar access system can be implemented using a cell phone, where a special number is called on the cell phone to make a purchase from a vending machine or gas pump. After the number is dialed, a special PIN number may be entered to verify the account holder's identity, and the machine of gas pump is unlocked (such as U.S. Pat. No. 6,535,726, issued Mar. 18, 2003, to Johnson).